Utility lines for water, electricity, gas, telephone, and cable television are often run underground for reasons of safety and aesthetics. In many situations, the underground utilities can be buried in a trench which is then back-filled. Although useful in areas of new construction, the burial of utilities in a trench has certain disadvantages. In areas supporting existing construction, a trench can cause serious disturbance to structures or roadways. Further, there is a high probability that digging a trench may damage previously buried utilities, and that structures or roadways disturbed by digging the trench are rarely restored to their original condition. Also, an open trench may pose a danger of injury to workers and passersby.
The general technique of boring a horizontal underground hole has recently been developed in order to overcome the disadvantages described above, as well as others unaddressed when employing conventional trenching techniques. In accordance with such a general horizontal boring technique, also known as horizontal directional drilling (HDD) or trenchless underground boring, a boring system is situated on the ground surface and drills a hole into the ground at an oblique angle with respect to the ground surface. A drilling fluid is typically flowed through the drill string, over the boring tool, and back up the borehole in order to remove cuttings and dirt. After the boring tool reaches a desired depth, the tool is then directed along a substantially horizontal path to create a horizontal borehole. After the desired length of borehole has been obtained, the tool is then directed upwards to break through to the earth's surface. A reamer is then attached to the drill string which is pulled back through the borehole, thus reaming out the borehole to a larger diameter. It is common to attach a utility line or other conduit to the reaming tool so that it is dragged through the borehole along with the reamer.
Another technique associated with horizontal directional drilling, often referred to as push reaming, involves attaching a reamer to the drill string at the entry side of a borehole after the boring tool has exited at the exit side of the borehole. The reamer is then pushed through the borehole while the drill rods being advanced out of the exit side of the borehole are individually disconnected at the exit location of the borehole. A push reaming technique is sometimes used because it advantageously provides for the recycling of the drilling fluid. The level of direct operator interaction with the drill string, such as is required to disconnect drill rods at the exit location of the borehole, is much greater than that associated with traditional horizontal directional drilling techniques.
The process of horizontal directional drilling has undergone significant development over the past two decades. These developments have involved the drilling machines and the location detection and directional control components. Several types of location detection and directional control systems have been utilized, with today's walk-over guidance systems becoming the most accepted technology. As the guidance/locator technology is quite different than the mechanical technology utilized in developing the drilling machines, in most instances companies have developed either the drilling machine or the guidance systems, but typically not both. As a result, there are now several suppliers of walk-over guidance systems, each with unique features, that are used with the variety of drilling machines.
Early in the development of horizontal directional drilling technology, it was recognized that there was a potential to incorporate location information, as generated from a remote electronic component and transferred via radio signals or hard wire, into the control of the drilling machines. Examples of this include U.S. Pat. Nos. 4,646,277 and 4,881,083, and GB 2175096, which are hereby incorporated herein by reference in their respective entireties. These systems were primarily configured as bore-to-target systems where the remote electronic component was placed at a position near a destination point. This remote electronic component then cooperated with the drilling machine, and specifically with an electronic component mounted in the drill head, with each individual component integral to the control system.
These systems provided varying degrees of success in directing a cutting tool to a target point, but did not provide accurate continuous information about the location of the cutting tool. Close monitoring of the cutting tool's location as it passes near to various underground objects at all points of the bore is generally considered critical to the overall process. Thus, the systems that operated in a manner to guide the cutting tool to a target turned out to be less useful than systems wherein cutting tool location was continuously monitored. These systems, referred to today as walk-over guidance systems, have been developed to provide a continuous or quasi-continuous monitoring capability. Several patents have been issued disclosing various aspects of the locating systems of the walk-over guidance systems, including U.S. Pat. Nos. 6,232,780; 6,008,651; 5,767,678; 5,880,680; 5,703,484; 5,425,179; 5,850,624; 5,711,381; 5,469,155; 5,363,926; and 5,165,490, which are hereby incorporated herein by reference in their respective entireties.
Other technologies are capable of providing information about travel of the drill head, including the use of gyroscopes, accelerometers, magnetometers, etc., in various types of dead-reckoning techniques or other techniques including establishing an electromagnetic field to be sensed by the drill head's electronics. In most cases, data from such sensors is typically transferred by what is known as a wire line, where an actual wire conductor extends within the drill pipe from the drilling bit back to the drilling machine. This wire enables transmission of data at higher rates than systems that rely on radio communications.
A major concern with this technology is accuracy, since as a borehole is extended a substantial distance, any small deviation at each reading point can be amplified, and if not corrected, eventually result in significant errors. One patent, U.S. Pat. No. 5,585,726, which is hereby incorporated herein by reference in its entirety, discloses a technique of utilizing both today's walk-over guidance technology and newer guidance technologies in conjunction. A difficulty in incorporating this technique is the variation in manufacturers of the wire line-based guidance packages which, when combined with variations in manufacturers of walk-over guidance systems, creates a situation where it will be difficult to integrate all necessary and/or desired information.
As the technology using walk-over guidance systems continues to evolve, the advantages of coordinating/integrating the information generated by the walk-over guidance systems into the overall control system of the drilling machine are becoming evident. A first step in this evolution has involved the transfer and display of information from the walk-over guidance systems to the drilling rig. Several patents disclosing this transfer of information have been issued, including U.S. Pat. Nos. 5,469,155; 5,711,381; 6,102,136; and 6,191,585, which are hereby incorporated herein by reference in their respective entireties.
Further integration developments include the capability of issuing machine commands to the drilling machine from a remote electronic component. Several patents disclosing such capabilities include U.S. Pat. Nos. 6,079,506; 6,279,668; and 6,408,952, which are hereby incorporated herein by reference in their respective entireties.
Another aspect of integrating the controls includes providing an indication of how the current location of the bore compares to the desired location, and providing a correction. Several exemplary patents include U.S. Pat. Nos. 5,698,981; 5,764,062; and 5,933,008, which are hereby incorporated herein by reference in their respective entireties.
Still further aspects of integration dealing with real time feedback and control are disclosed in various U.S. patents and U.S. and PCT applications including U.S. Pat. Nos. 6,308,787; 6,315,062; now U.S. Pat. Nos. 6,491,115; 5,778,991; 5,720,354; 5,819,859; 5,904,210; 6,161,630; 6,435,286; published PCT application WO 01/51760 A2; U.S. Pat. Nos. 6,250,402; 6,095,260; 6,047,783; 6,035,951; 6,191,585; 6,160,401; and 6,014,026, which are hereby incorporated herein by reference in their respective entireties.
Integration of the controls is ultimately aimed at enabling the actual boring process to remain on plan. Several patents disclosing various aspects involved with establishing a bore plan and then performing the bore, including location determination and machine control, have been issued, including U.S. Pat. Nos. 6,389,360 and 6,308,787; which are hereby incorporated herein by reference in their respective entireties. As bore planning becomes more common, there will be a continued desire to provide the maximum flexibility in how the bore plans are developed, how they are displayed to the operators, to allow on-the-fly adjustments of the bore plan, and increase the interactive aspects of bore planning. The interactive aspects should include the capability of the system to provide recommendations of appropriate actions.